Moreover, both CSF p‐NfH and NfL levels were significantly lower in SMA type 3 patients compared with intermediate‐progressing (3.19 ng/mL, P = .0008 and 4641.29 pg/mL, P < .0001) and fast‐progressing ALS patients (5.827 ng/mL, P < .0001 and 6369.44 pg/mL, P < .0001). Here, NEFL is linked to amyotrophic lateral sclerosis.